The Battle of Norditi (German: Schlacht bei Norditi), Battle of Nordendi (Schlacht von Nordendi) or Battle of Hilgenried Bay (Schlacht an der Hilgenrieder Bucht) was a battle between a Frisian army under Archbishop Rimbert of Bremen-Hamburg and an army of Danish Vikings in 884, which resulted in the complete withdrawal of the Vikings from East Frisia.
The first known record of the battle was written down in the same year in the Annales Fuldenses on 25 December 884, where, in a short note, a battle between the Frisians and Normans in the gau of Norditi (in loco, qui vocatur Norditi) is mentioned, in which the latter had been defeated. The localisation of this gau as the area that later became Norderland appears to be very likely, even though the town of Norden may not have existed at this point in time. The annals further record that Archbishop Rimbert had composed a letter about the events to Archbishop Liutbert of Mainz, which has not survived however. It is possible that church historian, Adam of Bremen, had this letter before him when he covered the battle in greater detail in the first book of his Gesta Hammaburgensis ecclesiae pontificum and named the place of the battle, in a slight spelling variation, as Nordwidi. The two medieval sources were later embellished in Ubbo Emmius' account in Rerum Frisicarum Historiae in 1546, without appearing to have any other sources to hand.
In the second half of the 9th century, Danish Vikings established bases on the East Frisian coast, from which they harassed the local population. Archbishop Rimbert of Bremen-Hamburg, who had had to break off his mission to the Vikings in Scandinavia, which had been begun by his predecessor Ansgar, was deeply concerned about this threat to the Church and the Empire. He therefore called on the Frisian population to resist the intruders and personally led them in the autumn of 884.